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Waltham Fields Community Farm (incorporated as Community Farms Outreach, Inc.) is a nonprofit farming organization focusing on sustainable food production, fresh food assistance, and on-farm education. For more information about Waltham Fields check out our website!

Wednesday, August 28, 2013

Notes From the Field - Las Plagas

Las Plagas. That's the phrase Dan and Erinn's old boss in California used to describe the travails of organic farming, and it's how Dan described all the pests and diseases to Hector when he started at our farm this spring. Little did we know how many of them we'd see in person this season.

Normally, we kind of lump las plagas together, since it's very difficult to know exactly what causes some of the problems we see in our crops on the farm without an official diagnosis from the lab at the University of Massachusetts. This season, however, we've been very fortunate to have Sue Scheufele, a vegetable specialist with UMass Extension, visiting every other week to take samples, check traps, and scout our crops in order to help us improve our organic production practices. This means that we know much more about the causes of the many pest and disease problems we've seen this season, and have a few more strategies for how to deal with them in upcoming seasons.

You've already heard in these notes about some of the major problems that Sue and other UMass specialists have helped us identify and create strategies for. Still, I thought I would run through a few of them in a little more detail for those of you keeping score at home. Here, in a nutshell, are some of the plagas that we've been dealing with at WFCF this season.

Late Blight: Its Latin name translates as "plant destroyer", and it was the cause of the Irish Potato Famine. This oomycete (not quite the same as a fungus) popped up from an unknown source in Eastern Massachusetts in late July this year. We have been spraying our big planting of field tomatoes at the Lyman Estate with a preventative combination of copper and bacterial and plant extracts, but we had left our PYO plants unsprayed to avoid the 24-hour break in harvesting that follows a spray application. It was a roll of the dice, and we got outsmarted by the disease this season. It appeared on August 9th in our cherry and plum tomatoes, and despite our efforts to contain it, spread to almost all of them by the 19th. While many organic growers, including us, tolerate some level of disease in our tomatoes, late blight is not one that we can live with. A few infected plants can create millions of spores that spread to other gardens and farms and destroy other crops and home harvests. So we don't let late blight stay on the farm, but do everything we can to destroy the plants and the disease as quickly as possible. Only one resistant variety of plum tomato (Plum Regal) and cherry tomato (Jasper) remain unaffected as of this writing, although we'll see what happens later in the season. What happens with late blight in the future? It's a good question. Right now it seems like a problem we're going to have to deal with each season, and something we need to think hard about how to manage in the future. We've already changed how we set up our tomato rows in order to facilitate spraying, and we are growing every resistant variety we can find. We need to continue to do research about how much spraying is really in the best interest of our soil and our health. We'll keep you updated!

Cucurbit Downy Mildew: When UMass entomologist Ruth Hazzard showed me the infected leaves, she said "this isn't your fault! This isn't your fault!" Downy mildew is a disease that blows in from the south every year and affects cucumbers and also, depending on the strain, other crops in the cucurbit family. It destroys plant leaves before fruit have a chance to mature, and can drastically shorten the harvest season for the crop. This year, downy mildew stopped our cucumber harvest this week, earlier than in previous seasons. As with late blight, about the only option available to an organic grower, besides the very important basics of growing a healthy plant in healthy soil, is regular applications of a preventative copper spray. This isn't something we've done for cucurbits in the past, but as with late blight, this disease isn't going to go away, and it's something we're going to need to be thinking about for the future. It's interesting to be facing two major crop diseases that aren't affected by crop rotation, since they can come in from off the farm each season. Stay tuned....

Basil Downy Mildew: Yes! Another new, destructive disease that appears to be here to stay! Basil downy mildew appeared in the United States in 2008, most likely from Uganda, according to researchers. Like late blight and curcurbit downy mildew, it spreads via wind-dispersed spores and makes its way through the country from areas where it overwinters each growing season. It causes yellowing of the lower leaves of the plant and eventually kills the crop, spreading from one succession to the next throughout the season. This is why we have been having you pull entire basil plants instead of picking sprigs, and why you may have noticed our basil crop looking a bit peaked this season. The solution? Yup, spray fungicides. There are a few organic fungicides that seem to be effective on this disease, and some types of basil, including Thai and red varieties, seem to be less affected. Still, here is another crop that used to be a sure thing, and one of the real joys of summer in New England like a beautiful ripe tomato or a crisp cucumber, that is now becoming more difficult to produce without the use of organic products from off the farm.

Flea Beetles: These have been around for a while, but have seemed particularly virulent this year. They are the tiny black beetles that hop around on crops in the brassica family, including kale, collards, broccoli, arugula, bok choy, broccoli raab, radish, and many more, putting tiny shot holes in the leaves of the crops and spreading diseases like Black Rot. This season they attacked our first planting of kale and collards so hard that, despite the fact that the plants were very healthy and well-nourished, they could not recover during the dry weather in July, and we had to take a break from these crops until our fall planting came on a couple of weeks ago. Our rutabaga crop, which we spent a great deal of time seeding in the greenhouse and transplanting in order to ensure that we'd actually get a crop this year, succumbed to black rot spread by flea beetles. We are monitoring our kale and collards, which are right across the farm road from the rutabaga, for the spread of the disease, which can also affect fall broccoli, cabbage and cauliflower. What can be done to protect crops? Resistant varieties are available, and clearly we're going to have to look into those; rotating fall brassicas away from spring brassicas actually does help with both flea beetles and the diseases they spread as well. But also, spraying pyganic to control the flea beetles, and to help control the disease, you guessed it, copper sprays. Plus they give the crop that nice patina. We haven't done any copper spraying in the brassicas yet, and we'll keep you posted.

Cucumber Beetle: This pest overwinters in the woods on the field edges and appears in the early cucumber and squash plantings. It gnaws on plants and fruit and spreads diseases (are you sensing a pattern here?) including bacterial wilt, which took down a good portion of our second cucumber planting this year. Again, resistant varieties help, as does rotating our cucurbit crop away from where it was the season before. We can also plant later successions away from earlier ones, although then we run into the larger rotational issue of having cucurbit family crops all over the farm. Here again, we have the final option of spraying pyganic, an organically approved but non-specific pesticide, if the population of beetles overwhelms our crop despite out best efforts. It's not a great option, but we did do it once this year.

Mexican Bean Beetle: This is a crop that can be particularly bad for organic growers with PYO bean crops who can't rotate beans to another field and plant small successions of beans over the course of the season. These are the copper-colored spotted beetles (related to ladybugs) and spiky yellow larvae that you have probably seen in the beans at some point this season. We've tried releasing pediobius wasps, a parasite of the bean beetle that lays its eggs in its larvae, but the progress that we are making there is hard to determine. We've done extensive scouting over the course of the season to determine the times when the pest is at its worst and spray pyganic, just before it looks like the population is about to explode. Again, it would be so much better if the biological control was effective, but we'll have to wait and see about that one.

Spotted Wing Drosophila (SWD): Several weeks ago, we started to spray the raspberries with spinosad, a compound made by bacteria that is approved for use in organic systems and is currently thought to be our best bet against the spotted wing drosophila. SWD was found in New England for the first time after Hurricane Irene, although it has been a pest in the South and Northwest for some time. It is unique among fruit flies in that it attacks sound fruit that is not overripe or damaged in any way, laying its eggs in the fruit and making it, although not harmful, definitely less palatable. In a survey this winter, you told us that you'd like to see us try to use every organic option at our disposal to save the berries, and so we are; turning in beds that weren't producing as well in order to consolidate our efforts, monitoring traps on the property to see when the population of SWD rises, and then spraying once a week for six weeks to see if we can get a crop that is relatively free of SWD larvae. So far, so good.

Weeds: Those of you who have been with us for a while (and who are still reading after all these plagas) may have noticed that the population of weeds on the farm was not as bad as it has been in the past. There are still a few trouble spots here and there, but by and large the weeds have not had the impact on our crops that they have had in previous seasons. This is partly a result of the very dry season, but partly a result of the incredible work done by this year's weed crew, who finished their official season with us last week. In various configurations, Alice, Sage, Eli, and Lizzie (seen below from left to right, with farmer Dan Roberts second from right) Ashley and Jesse hoed and weeded their way through nearly every crop on the farm. There's definitely a relief in the knowledge that with all these crazy pests and diseases popping up all over the farm, some of our biggest challenges can be solved on hands and knees, and with simple tools that have been around since before the industrial revolution. The difference they made is showing itself in our yields and in the quality of our produce. We are deeply grateful.

Enjoy the harvest, Amanda, for the farm staff

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